1. Field Of The Invention
This invention lies in the field of polyols useful in formulating resin prepolymer blends for reaction with organic isocyanates to produce polyurethane and/or polyurethanepolyisocyanurate cellular polymers, and, more particularly, in the field of polyester polyols based on dimethyl terephthalate residues which polyols are compatible with high levels of fluorocarbon blowing agents.
2. Prior Art
Aromatic polyester polyols are coming into widespread usage in the manufacture of polyurethane and polyurethanepolyisocyanurate foams. Such polyester polyols are attractive because they tend to be low in cost, yet can produce rigid cellular polymers of excellent properties adapted for many end use applications.
One class of aromatic polyester polyols which has recently become commercially available comprises esters produced by esterifying phthalic acid or phthalic acid anhydride with an aliphatic polyhydric alcohol. For example, a diethylene glycol phthalate is available commercially from Stepan Company, Northfield, Ill. Such liquid product has a desirably low viscosity, a desirably high aromatic ring content, and a desirably low acid number. Even though such product typically has a reactive hydrogen functionality of less than about 3, it catalytically reacts well with organic isocyanates to produce, for example, rigid cellular polyurethane-polyisocyanurate polymers that can have commercially acceptable characteristics.
Another class of aromatic polyester polyols which has recently become commercially available comprises esters produced by reacting polyethylene terephthalate (PET) with alkylene polyols. For example, scrap or waste PET can be digested (glycolized) with a diol or triol as taught by Svoboda et al U.S. Pat. No. 4,048,104, or transesterified with a residue from dibasic acid manufacture as taught by Brennan in U.S. Pat. No. 4,439,550, or the like, to produce a polyester polyol product which catalytically reacts well with organic isocyanates to produce, for example, rigid cellular polyurethane-polyisocyanurate polymers that can have commercially acceptable characteristics.
A further class of aromatic polyester polyols which has recently become commercially available comprises esters produced by reacting dimethyl terephthalate (DMT) residues with alkylene polyols. For example, in DeGuiseppi et al U.S. Pat. No. 4,237,238 a DMT residue obtained from the manufacture of dimethyl terephthalate is transesterified with a glycol of molecular weight ranging from about 60 to 400 and the resulting polyol is reacted with isocyanates to produce polyisocyanurate foams alleged to have a high degree of fire resistance with low smoke evaluation. See also, for examples, Walker U.S. Pat. No. 3,647,759, Grube et al U.S. Pat. No. 4,444,917, Grube et al U.S. Pat. No. 4,444,916, Grube et al U.S. Pat. No. 4,444,915, Anderson U.S. Pat. No. 4,469,821, and Zimmerman U.S. Pat. No. 4,442,238.
One problem with most such commercially viable aromatic polyester polyols is that they characteristically are poorly compatible with fluorocarbon compounds of the type conventionally used as blowing agents to make such cellular polymers.
The usual solution to this problem has been to admix with such a polyol a separately formed compatibilizing agent in an amount sufficient to produce a resulting mixture with a desired amount of compatibility (solubility) for fluorocarbons. For examples, Koehler et al U.S. Pat. No. 4,246,364 use a class of amide diols, while Wood U.S. Pat. No. 4,529,744 issued July 16, 1985 uses a combination of relatively high molecular weight propoxylate ethoxylate compounds with amine and/or amide diol compounds. The amide diols employed by Wood are similar to those taught by Koehler et al. The propoxylate ethoxylate compounds employed by Wood are, in fact, similar to those employed in practicing the present invention, as hereinbelow described.
The necessity to compound a fluorocarbon compatibilizing agent with aromatic polyester polyol means an extra cost in the formulation of a so-called resin prepolymer blend. Such resin prepolymer blends are conventionally employed in the trade for reaction with organic isocyanates to produce polyurethane and/or polyurethane-polyisocyanurate cellular polymers. Resin prepolymer blends are uniform, homogeneous liquid compositions comprised of polyol, urethane-forming and/or isocyanurate-forming catalyst, fluorocarbon blowing agent, other optional additives, and, in the case of aromatic polyester polyols, a fluorocarbon compatibilizing agent, as is well known to those skilled in the art. A desired quantity of a compatibilizing agent is blended with an aromatic polyester polyol before such fluorocarbon is added, and such a blending step itself adds to the cost of resin prepolymer blend manufacture.
However, the cost of a compatibilizing agent is even more significant. Moreover, the costs of such an agent are escalating. For example, the cost of the cochin oil, which is used as a starting material to make an amide diol as above identified, increased by approximately 60 percent in price in 1984. Unless the cost of producing resin prepolymer blends of aromatic polyester polyols can be controlled and maintained at economically competitive levels, aromatic polyester polyols will not have a commercial place in this field.
There is a need for fluorocarbon compatibilized aromatic polyester polyols which not only are economical to produce, but also are convertible into cellular foams having excellent properties.
Aromatic polyester polyols, especially polyols based on residues from the manufacture of dimethyl terephthalate are producible by transesterification of dimethyl terephthalate residues as referenced above. The idea of somehow modifying the reaction components without substantially increasing costs so as to result in a polyol product that is directly compatible (self-compatibilized) with fluorocarbons is certainly attractive. Not only would this avoid the need for a separate compatibilizing agent admixing step, but also this could avoid the cost of an added compatibilizing agent.
So far as is known, no one has heretofore produced a class of polyester polyol blends based on dimethyl terephthalate residues which is both fluorocarbon self-compatibilizing, and produces polyurethane and polyurethane-polyisocyanurate foam with improved properties. Such a polyester polyol can be formulated into a resin prepolymer blend and then reacted with organic isocyanate to produce cellular polyurethane-polyisocyanurate type polymers of generally commercially acceptable quality.